Sheet feeder

ABSTRACT

A device for feeding sheets of paper or the like from a pile of such sheets, the device comprising means for lifting a pile of sheets; first means for sensing the height at the front margin of the top sheet of such pile; lifting, separating and suction means at the rear margin of said pile; means arranged at the front margin of said pile for receiving and transferring the sheets one after the other from said pile; second sensing means for sensing the height of the pile at its rear margin; control means for stepwise changing the height of the separating and lifting means at the rear margin of the pile of sheets under the influence of said first sensing means; and means operated by said lifting means controlling the raising of said pile so as to hold also its front margin at the proper height for the reception of the top sheet by said receiving and transferring means.

United States Patent [191 Kistner SHEET FEEDER [75] Inventor: Hermann Kistner, Neckarweihingen, Germany [73] Assignee: Maschinebau Qppenweiler GmbH,

oi' fi'weiif near Backnang, l e rmany [22] Filed: Nov. 23, 1970 [21] Appl. No.: 91,702

[52] US. Cl. ..271/31, 271/62 R [51] Int. Cl. B65h 1/18 [58] Field ofSearch.....217/30 R, 31, 62 R, 62 A, 24,

[4 1 Feb. 13, 1973 Attorney-Stowell and Stowell [5 7] ABSTRACT A device for feeding sheets of paper or the like from a pile of such sheets, the device comprising means for lifting a pile of sheets; first means for sensing the height at the front margin of the top sheet of such pile; lifting, separating and suction means at the rear margin of said pile; means arranged at the front margin of said pile for receiving and transferring the sheets one after the other from said pile; second sensing means for sensing the height of the pile at its rear margin; control means for stepwise changing the height of the separating and lifting means at the rear margin of the pile of sheets under the influence of said first sensing means; and means operated by said lifting means controlling the raising of said pile so as to hold also its front margin at the proper height for the reception of the top sheet by said receiving and transferring means.

12 Claims, 5 Drawing Figures PAIENTEU I 31975 3.716.226

sum 2 or 4 Fig. 2

SHEET FEEDER BACKGROUND OF THE INVENTION The invention relates to a device for feeding sheets of paper, cardboard or other materials from a pile of sheets, in which lifting and separating means are provided at the rear margin of the pile, in which receiving and transferring means for the sheets are provided at the front margin of the pile, in which means are provided for lifting the pile of sheets; in which control means are provided for adjusting the lifting of the pile of sheets so that its front edge is at the proper height relative to said receiving and transferring means.

Devices of this type serve for delivering the sheets of the pile one after the other to a printing, folding or other sheet handling machine.

A serious and difficult problem arises with such sheet feeders from the fact that the height or level of the sheet at the front and at rear margin, respectively, of the pile are often different on account of printing on the sheets, which printing on each individual sheet may be ever so thin but which in a pile of sheets adds up to such an extent that there are often several inches of difference in height between the front edge and the rear edge of the pile. It will be easily understood that this difference of height is greater when the pile still contains a maximum number of sheets and that this difference becomes smaller and smaller as sheets are taken off the pile and the number of sheets decreases more and more.

It is well known and has long since been recognized that time consuming and correspondingly expensive manual preparations of the pile are required so as to adjust such height differences by means of wedges slid into the pile of sheets. These corrections have moreover to be repeated several times so as to adjust for the diminishing difference in height as the number of sheets in the pile decreases.

Proposals are known for automatically effecting the adjustments in height. German Pat. No. 1,1 10,657, for instance, discloses a device which is to take care of the differences in height of the pile by a control device connected with a lever of the suction head on the rear margin of the pile and by controlling the height position of the suction head according to the position of the pile surface. This type of height control is disadvantageous for fast running machines because the working of the control element has to be adjusted by necessity according to the speed of movement of the suction head which practically stops within a working circle about half the time in the upper position and then has to carry out its lifting stroke in a very short period of time so as to lift and air the next sheet. This rhythm of movement,

determined by the function of the suction head, is unfavorable for the control of the height position. This known device leads, for reasons which need not to be explained at the greater length here, to vibrations limiting the speed of the working cycle and at high speeds to malfunctioning.

OBJECTS OF THE INVENTION A primary object of the invention is the provision of a height adjustment control for the indicated type of sheet feeders, which is adapted to the speed with which modern suction heads are able to operate.

A more specific object of the invention is the provision of a height adjustment control which does not impede the efficiency of the rear sheet separating means but improves their operation.

OUTLINE OF THE INVENTION According to the present invention there is employed a sheet separating apparatus, which may be of prior known construction, carrying only the required sheet separating means such as suction device, hold-down feeler, strip-off brushes and blowing jets. The movements of the suction device as well as of the hold-down feeler are exclusively determined by the purpose of their use. In the lower rest position of the holding element, that is in the position in which the holding-down feeler rests resiliently on the pile below the lifted off sheet and holds the uppermost sheet of the pile against displacement during the operation of the blowing jets, this feeler actuates, in response to the pile height being slightly lowered on account of the sheet removal, a contact which triggers a lifting of the pile by a predetermined small amount via an electromotor, pawl-andratchet devices or a magnetic coupling. On account of this aftercontrol of the pile, the sheet separating apparatus remains therefore always in the correct working height relative to the same and the suction devices reach always the next uppermost sheet of the pile by a constant stroke.

The differences in the height positions of the pile between its front and the rear margins are, according to the present invention, determined by an independently moved feeler on the front edge, which preferably rests on each second sheet of the pile and therefore needs to work with half the speed only as the feeding device. This feeler can in case of an uneven pile determine a height which is, relative to the front sheet separating or sheet transfer means, too great, correct or too small, respectively. Whereas no order is given when the pile height at the front edge is correct, a correcting control is triggered by mechanical, electrical, optical or pneumatic means when the location of the pile surface deviates from the normal one. This correcting or aftercontrol is carried out according to the present invention by lifting or lowering, respectively, by a small amount, the entire frame supporting the rear separating means via a shaft with bevel gears, a motor or a hydraulic control. This correction is then automatically followed by the aftercontrol of the pile height, which controls in a know manner the correct working height of the pile relative to the rear separation means. Hereby the independence of the equalization control is achieved and the limitation or reduction of the efficiency of the sheet separating, as it would occur upon its coupling with sensitive controls, is avoided.

So as to avoid proneness of the device to malfunctioning, the control of the independent front pile sensor works, according to the present invention, at half speed, i.e., so that after each second sheet only a sensing or after-control, respectively, is carried out. This is more than sufficient because very small corrections only are necessary.

A further advantage of the invention resides in the fact that the rear sheet separating means are firmly connected at a short distance with its suspension and its driving means and that this rigid securement eliminates vibrations and permits essentially higher outputs.

A further advantage, as compared to the known devices, resides therein that according to the invention it is possible to mount the known suction lifting and separating means on the supporting frame which means without rhythm and without drive and permit a very high sequence of sheets. Such devices are specially favored for small sheet sizes; they operate on account of the after-control of the pile in a known manner and with constant stroke of the suction means. For universal machines, i.e., those adapted for handling a large range of sheet sizes, a lifting suction and separating unit suitable for small sizes may be mounted in place of or additionally in front of the normal separating unit assembly so as to operate the machine for each sheet length at maximum effectiveness.

Because a large number of sheet feeders are in use in connection with known separating units having lifting suction devices or controlled separating units with sheet sensors, respectively, the device according the present invention is made suitable for installation in these known machines and is capable of rendering these sheet feeders more efficient in a simple manner without a change of their separating units.

The suspension frame may be constructed in various ways and may change its height position by vertical guides or by pivotal movements. This change of height may be controlled for instance via a shaft with ratchet wheel, by motor or by hydraulic means. The suspension frame carries the mounting rail for the separating unit which is adjustable according to the length of the sheet size. The frame also carries the driving shaft for the separating unit, the shaft being preferably formed as a profiled shaft so that it retains its driving connection with the separating unit at any position of the latter.

ILLUSTRATION AND DESCRIPTION OF A PREFERRED EMBODIMENT The aforesaid and further objects, advantages and features of the invention will be more fully understood from the following description of a preferred embodiment of the present invention as well as from its illustration in the attached drawings.

In the attached drawings:

FIG. 1 is a diagrammatic three-quarter rear and side perspective view of a sheet feeder incorporating the features of the present invention;

FIG. 2 is a diagrammatic side elevation of the feeder shown in FIG. 1;

FIG. 3 is a fragmentary side elevation of the front margin of a pile of sheets and of the sensor engaging such front margin;

FIG. 4 is a diagrammatic illustration of the means for driving the rear separating unit and the front sensing unit;

FIG. 5 is a diagrammatic side elevation of the rear separating unit, its walls being partly broken away to show the interior mechanism.

As diagrammatically shown in FIG. 1, there is a foundation or floor on which is supported a framework comprising vertical columns 12, 14, l6, l8 and 20, these columns being interconnected by transverse elements 22 and 24 as well as by other longitudinal and transverse frame members which are not illustrated as having no bearing on the invention. It will for instance be noted that even the column 12 is broken off before its connection with the transverse element 22.

A customary horizontal table 26 supports a pile 28 of sheets of papers or any other material. The sheets may carry heavy imprint 30 near the front edge adjoining the frame member 24, which leads to a difference D (FIG. 2) between the height r level at the front edge and the rear edge of pile 28.

Table 26 is supported by chains 32 trained around idler pulleys 34 rotatably mounted on members of the machine frame, such as column 12, and around drive pulleys 36. The pulleys 36 are drivingly connected with worm-gears 38 which in turn are engaged by a shaft 40 driven by a (not shown) motor. A shaft 42 drives not only one of the drive pulleys 36 but also a pulley 44 which latter drives by means of an intermediate chain 46 the pulley 36 for the chain 32 visible near the right forward side in FIG. 1. The construction of table 26, of its supporting chains 32, of the means for driving the chains 32 and of associated elements need not be illustrated and described in greater detail as they are well known to those skilled in the art. It suffices to say that a sheet lifted from the pile 28 is received and transferred by a well known suction wheel 48 and thence to an ad joining machine which is merely diagrammatically indicated in FIG. 1 by the surface 50.

The height of the front margin of the top sheet of stack or pile 28 relative to suction wheel 48 is adjusted by the movement of table or plate 26 carrying said stack 28. The movement of table 26 is controlled by the cooperation of a feeler assembly 52 at the front end of stack 28 and a separation assembly 54 at the rear end of stack 28.

As illustrated in FIGS. 1 and 3, the front feeler assembly 52 comprises the feeler 56 engaging the top surface at the front of stack 28. This feeler 56 consists of an elongated, approximately vertically arranged member 58 pivoted at 60 to a link 62, the latter in turn being pivoted at 64 to a stationary part 66 of the machine frame. Member 58 carries a cam follower 68. A tension spring 70 is inserted between the lower end of member 58 and a stationary part 72 of the machine frame. Cam follower 68 is held by spring 70 in engagement with a cam 74 fixedly mounted on a rotatable shaft 76. Shaft 76 carries two further earns 78 and 80 of which cam 78 is adapted to engage a cam follower 82 arranged on link 62 between its pivots 60 and 64. Cam 80 is adapted for engagement with a trigger pin 84 of an impulse switch 86, the function of which will be explained later on. The lower end of lever or arm 58 carries a contact point 88 which, depending on the still to be explained momentary position of lever 58, engages either one of two stationary contacts 90 or 92 or neither one of these contacts.

The suction or separating assembly 54 is carried, as shown in FIG. 1, by a bar 94 forming an integral part of a frame 96 guided for vertical up and down movement by conventional, not illustrated means on the columns 14 and 16 of the machine frame. The assembly 54 is slideable on the bar 94 and may be secured on it at any desired location by a screw 98. Frame 96 is integrally connected at two of its corners with hollow, interiorly screw threaded shafts 100 the lower ends of which are engaged by outwardly screw threaded shafts 102. The lower ends of shafts 102 are drivingly connected by bevel gears 104 with the drive shaft 106 of a motor 108. It is apparent that the motor 108, depending on its direction of rotation, will either raise or lower frame 96 with unit 54 or that frame 96 will be kept stationary when the motor 108 is standing still.

A profiled sheet 110 paralleling bar 94 is rotatably supported at its ends in frame 96. This shaft 110 is rocked about a certain angle by a link 112 inserted between lever 114 on shaft 110 and bevel gear 116, the latter meshing with bevel gear 118 on shaft 120. As shown in FIG. 4, gear 116, pinion 1 18 and shaft 120 are rotatably supported in frame 96. Shaft 120 is telescopingly and drivingly engaged by hollow shaft 122 which in turn is driven via gears 124, 126 by a shaft 128. Shaft 128 drives via bevel gear 130 the herein before described shaft 76 of the front feeler assembly 52. Shafts 122, gears 124, 126, 130 and shaft 76 are rotatably supported in parts of the stationary machine frame. The telescoping shafts 120, 122 permit upward and downward movement of shaft 110 without interrupting the driving connection with shaft 128. Of course, the driving connections between shaft 76, shaft 128 and shafts 122 and 124, which is diagrammatically illustrated in FIG. 4, may also be carried out by other well known means. Shaft 128 may either be driven by an adjustable-speed motor or it may be coupled with the drive mechanism of the machine following the new feeder so as to assure that the machine is fed at its working speed with sheets from stack 28.

As likewise shown particularly in FIG. 5, shaft 110 extends through housing 132 of the separating assembly 54. Within the housing 132 the shaft 110 carries a lever 134 having an opening mating the outer profile of shaft 110. Lever 134 slidingly engages shaft 110 so that movement of the housing along bar 110 will allow the lever 134 to move along shaft 110 without interrupting the driving connection between shaft 110 and lever 134. The outer free end of lever 134 carries a ball-bearing 136 or the like which fits between projections 138 of an elongated slide element 140 guided for up and down movement in the housing 132. Evidently, rocking of shaft 110 will impart a reciprocating movement to slide 140 by means of lever 134 and ball-bearing 136.

As shown particularly in FIGS. 4 and 5 the lower end of slide 140 extends to the outside of housing 132 and carries one or more suction cups 142. The cups are connected by hoses 144 with a source of vacuum (not shown). A lever 146 is pivoted at 148 in housing 132. A short arm 150 of lever 146 carries a cam follower 152, held in engagement with cam surface 154 on slide 140 by a compression spring 156 inserted between lever 146 and a stationary part 158 of housing 132. Pivoted at 160 to lever 146 is an elongated feeler element 162 having its lower end 164 extended through an opening in housing 132 and bent off for engagement with the top surface of the stack of sheets 28. Springs 166 and 168 are inserted respectively between feeler 162 and a part of housing 132 and between a point of lever 146 remote from the pivot connection 160 and lever 162.

When slide 140 moves upwards, lever 146 and feeler 162 are permitted to move downwardly and inwardly under the influence of springs 156, 166 and 168 due to the engagement of cam follower 152 with a recessed portion of cam surface 154. When feeler 162 is moved upwardly its bent off lower end 164 engages a roller 170 on housing 132 and is thereby forced laterally away from stack or pile 28. If the distance between housing 132 and top of pile 28 reaches a certain predetermined size, lever 146 will move down so far that its outer end 172 engages and triggers a pin 174 of a switch 176. Switch 176 is connected via conductor 178 with the motor (not shown) driving the lifting chains 32 for table 26 carrying the pile 28. This is diagrammatically illustrated in FIG. 2.

Rotation of shaft 76 causes the front feeler 56 to engage the forward margin of pile 28 under the influence of cam surfaces 74 and 78 and cam followers 68 and 82. Depending on whether the front surface of pile 28 is too high or too low, point 88 will make contact with one of the switches or 92 and cause motor 108 either to raise or to lower frame 96 carrying the separating assembly 54, which in turn will lead to a raising or lowering of the platform 26 carrying the pile 28 under the influence of switch 176. So as to prevent actuating of motor 108 each time when contact 84 passes the switches 90, 92 in the course of the up and down movement of feeler 56, 58 into and out of engagement with top of pile 28, the switches 90, 92 are supplied with current in the engagement position of feeler 56, 58 only by means of impulse switch 86, the pin 84 of which engages the cam 80.

It should be understood that the surface of the pile 28 at its front margin should be kept at an essentially constant height or level relative to the floor l0 and all stationary parts of the machine frame. This height 180 should not vary more than :3 mm (FIG. 3). If this variation is exceeded, then the adjustment operations are started through feeler 56 and contacts 90, 92 and 88.

While a particular embodiment of the invention has been shown and described, it will be understood that various modifications may be made without departing from the true spirit and scope of the invention. The appended claims are, therefore, intended to cover any such modifications.

What is claimed is:

1. In a device for feeding sheets from a pile of sheets, said device comprising: means for lifting a pile of sheets; lifting, separating and suction means at the rear margin of said pile; means arranged at the front margin of said pile for receiving and transferring the sheets one after the other from said pile; sensing means for sensing the height of the pile at its front margin; control means for stepwise changing the height of the separating and lifting means at the rear margin of the pile of sheets under the influence of the said sensing means; and means operated by said lifting means controlling the raising of said pile so as to hold also its front margin at the proper height for the reception of the top sheet by said receiving and transferring means.

2. In a device according to claim 1, additionally comprising a first moving means for moving said lifting, separating and suction means up and down away from and toward the top of said pile of sheets; a second moving means for moving said sensing means up and down away from and toward the top of said pile of sheets; a common means for rythmically and synchronously driving said first moving means and said second moving means.

3. In a device according to claim 2 comprising additionally: a gear means coupling said first and said second moving means and driving said second moving means at a speed being a fraction of the speed of said first moving means.

4. In a device according to claim 3, said gear means being adapted to drive said second moving means at one half the speed of said first moving means.

5. In a device according to claim 2, in which said second means comprises a shaft; three cams secured on said shaft; a machine frame; a sensor element floatingly suspended von said frame permitting upward and downward movement of said sensor element as well as horizontal movement toward and away from said pile; two contacts fixedly supported relative to said frame; a contact on said sensor element adapted to engage one or the other of said contacts; a pair of cam followers associated with said sensor element engaging one each of two of said cams for effecting the upward and downward movement and the horizontal movement of said sensor element; a third cam follower in the form of a switch operator engaging the third cam to control a switching means; the arrangement being such that said third cam follower and its cam operate said switching means when said other two cam followers and earns have moved the sensor element into its lowermost position and toward said pile in engagement with the top surface of said pile at the latters front margin.

6. In a device according to claim 5, in which said sensor element is spring biased into engagement of its said cam followers with the respective ones of said cams.

7. In a device according to claim 1, in which said lifting, separating and suction means comprise a housing; a first element guided in said housing for upward and downward movement and carrying a suction cup adjacent its lower end; a first sensor element guided on said housing for upward and downward movement; means adapted to impart said upward and downward movement to both said first element and said sensor element; a machine frame; means supporting said housing permitting upward and downward movement thereof relative to said machine frame; drive means for imparting such upward and downward movement to said housing; said drive means being actuated by said sensing means.

8. In a device according to claim 7, in which said supporting means comprise a second frame guided on said machine frame for upward and downward movement; a horizontal guide of said second frame carrying said housing and permitting its movement in a direction toward and away from said sensing means; a horizontal shaft rotatably supported by said second frame and being connected to a source of power for angular rocking movement of said shaft about its longitudinal axis; and a driving connection between said shaft and said first element for imparting movement from said shaft to said first element while permitting movement of said housing with said first sensor element along said horizontal guide and said shaft.

9. In a device according to claim 7, additionally comprising: a switch carried by said housing, means on said sensor element adapted to energize said switch upon the movement of said sensor element exceeding a predetermined amount; said switch controlling said means for lifting a pile of sheets.

10. In a device according to claim 7, additionally comprising: a motor constitutin said drive means; a first contact and a second con act fixedly supported relative to said machine frame; a second sensor element forming part of said sensing means for sensing the height of said pile at its front margin; means for moving said second sensor element up and down into and out of engagement with the top of said pile; a third contact on said second sensor element adapted to engage one of said first and second contact elements depending on the position of said sensor element upon engaging the top of said pile; and electric conductors between said contacts and said motor adapted to cause the motor to move in one of its two directions of rotation and lift and lower respectively said housing.

11. In a device according to claim 10, additionally comprising: switching means interposed in the circuits including said motor and said three contacts; and means for closing said switching means only upon said second sensor element being in the position of sensing the height of said pile.

12. In a device according to claim 1, in which a second sensing means senses the height of the pile adjacent its rear margin and constitutes part of said means controlling the raising of said pile; and in which said first named sensing means for sensing the height of the pile at its front margin and said second sensing means constitute the sole means for sensing the heights of the pile adjacent its front and rear margins to the exclusion of any means for determining the difference between said two heights. 

1. In a device for feeding sheets from a pile of sheets, said device comprising: means for lifting a pile of sheets; lifting, separating and suction means at the rear margin of said pile; means arranged at the front margin of said pile for receiving and transferring the sheets one after the other from said pile; sensing means for sensing the height of the pile at its front margin; control means for stepwise changing the height of the separating and lifting means at the rear margin of the pile of sheets under the influence of the said sensing means; and means operated by said lifting means controlling the raising of said pile so as to hold also its front margin at the proper height for the reception of the top sheet by said receiving and transferring means.
 1. In a device for feeding sheets from a pile of sheets, said device comprising: means for lifting a pile of sheets; lifting, separating and suction means at the rear margin of said pile; means arranged at the front margin of said pile for receiving and transferring the sheets one after the other from said pile; sensing means for sensing the height of the pile at its front margin; control means for stepwise changing the height of the separating and lifting means at the rear margin of the pile of sheets under the influence of the said sensing means; and means operated by said lifting means controlling the raising of said pile so as to hold also its front margin at the proper height for the reception of the top sheet by said receiving and transferring means.
 2. In a device according to claim 1, additionally comprising a first moving means for moving said lifting, separating and suction means up and down away from and toward the top of said pile of sheets; a second moving means for moving said sensing means up and down away from and toward the top of said pile of sheets; a common means for rythmically and synchronously driving said first moving means and said second moving means.
 3. In a device according to claim 2 comprising additionally: a gear means coupling said first and said second moving means and driving said second moving means at a speed being a fraction of the speed of said first moving means.
 4. In a device according to claim 3, said gear means being adapted to drive said second moving means at one half the speed of said first moving means.
 5. In a device according to claim 2, in which said second means comprises a shaft; three cams secured on said shaft; a machine frame; a sensor element floatingly suspended on said frame permitting upward and downward movement of said sensor element as well as horizontal movement toward and away from said pile; two contacts fixedly supported relative to said frame; a contact on said sensor element adapted to engage one or the other of said contacts; a pair of cam followers associated with said sensor element engaging one each of two of said cams for effecting the upward and downward movement and the horizontal movement of said sensor element; a third cam follower in the form of a switch operator engaging the third cam to control a switching means; the arrangement being such that said third cam follower and its cam operate said switching means when said other two cam followers and cams have moved the sensor element into its lowermost position and toward said pile in engagement with the top surface of said pile at the latter''s front margin.
 6. In a device according to claim 5, in which said sensor element is spring biased into engagement of its said cam followers with the respective ones of said cams.
 7. In a device according to claim 1, in which said lifting, separating and suction means comprise : a housing; a first element guided in said housing for upward and downward movement and carrying a suction cup adjacent its lower end; a first sensor element guided on said housing for upward and downward movement; means adapted to impart said upward and downward movement to both said first element and said sensor element; a machine frame; means supporting said housing permitting upward and downward movement thereof relative to said machine frame; drive means for imparting such upward and downward movement to said housing; said drive means being actuated by said sensing means.
 8. In a device according to claim 7, in which said supporting means comprise : a second frame guided on said machine frame for upward and downward movement; a horizontal guide of said second frame carrying said housing and permitting its movement in a direction toward and away from said sensing means; a horizontal shaft rotatably supported by said second frame and beiNg connected to a source of power for angular rocking movement of said shaft about its longitudinal axis; and a driving connection between said shaft and said first element for imparting movement from said shaft to said first element while permitting movement of said housing with said first sensor element along said horizontal guide and said shaft.
 9. In a device according to claim 7, additionally comprising: a switch carried by said housing, means on said sensor element adapted to energize said switch upon the movement of said sensor element exceeding a predetermined amount; said switch controlling said means for lifting a pile of sheets.
 10. In a device according to claim 7, additionally comprising: a motor constituting said drive means; a first contact and a second contact fixedly supported relative to said machine frame; a second sensor element forming part of said sensing means for sensing the height of said pile at its front margin; means for moving said second sensor element up and down into and out of engagement with the top of said pile; a third contact on said second sensor element adapted to engage one of said first and second contact elements depending on the position of said sensor element upon engaging the top of said pile; and electric conductors between said contacts and said motor adapted to cause the motor to move in one of its two directions of rotation and lift and lower respectively said housing.
 11. In a device according to claim 10, additionally comprising: switching means interposed in the circuits including said motor and said three contacts; and means for closing said switching means only upon said second sensor element being in the position of sensing the height of said pile. 